This invention relates to a rotor of a superconductive rotary electric machine in which laminated coil protective covers composed of a plurality of thin cylindrical plates are placed between the end parts of the superconducting field coils and the coil holder rings that are mounted at both ends of a coil mounting shaft. The main function of the protective covers is to transmit to the holding rings centrifugal or electromagnetic forces and thermal stressed exterted on the holding rings and on the electrical insulation between the field coils and the holding rings and to firmly support said coils. Accordingly, the covers are required to have a thickness of the order of several millimeters.
A conventional protective cover is shown in FIG. 1 and is composed of a pair of semicylindrical insulating segments connected to each other to form a cylinder which is several tens of centimeters in diameter.
The cover is made of two semicylindrical segments because the coil mounting shaft has an outside diameter larger than the inside diameter of the protective cover and hence a cover formed as a one-piece cylinder can not be mounted in position on the mounting shaft.
The protective cover 22 is constructed of a cast or poured insulating material. However these covers are costly because of the expenses involved in machining and molds. In addition, accurate machining is required for machining a protective cover from a blank of insulating material.
Moreover, the peripheral surface of the cover must be made truly circular because the holder ring is fitted on the peripheral surface of the coil end portions. In case of mismatching between the superconducting field coils and the insulating cover, there is produced a gap between the coils and the cover, and difficult operations may be required in machining the semicylindrical insulators to a true circular shape. In any case, a large quantity of an adhesive must be used in the manufacture of the prior-art protective cover 22 and the true circular shape of the cover 22 must be maintained by the use of a compacting tool and by a painstaking assembly operation.